Method for the dehydrogenation of dichlorosilane

ABSTRACT

Dichlorosilane and trichlorosilane are dehydrogenated at elevated temperature in the presence of an ammonium or phosphonium salt as a catalyst, and a halogenated hydrocarbon or hydrogen halide. The method may be used to synthesize organochlorosilane.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of PCT Appn. No.PCT/EP2018/073933 filed Sep. 6, 2018, the disclosure of which isincorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for the dehydrogenation ofdichlorosilane, wherein dichlorosilane is reacted in the presence of anammonium and/or phosphonium salt either with at least one halogenatedhydrocarbon or with a hydrogen halide.

2. Description of the Related Art

Organohalosilanes and especially organotrihalosilanes are used ashydrophobing agents or as starting materials for organosilanes.Organosilanes or organofunctional silanes are hybrid compounds thatcombine the functionality of reactive organic groups with the inorganicfunctionalities of alkyl silicates. They can be used as molecularbridges between organic polymers and inorganic materials. Anotherapplication of industrial importance is use as a component of silicones.

The sole ways of efficiently constructing C—Si bonds on a large scalehave up to now been hydrosilylation and the Müller-Rochow process.Hydrosilylation always requires a double bond or triple bond on theorganic radical and an Si—H group so that a Si—C bond can be created.The Müller-Rochow process is based on elemental silicon and simpleorganochlorine compounds such as MeCl. Temperatures of approx. 300° C.are necessary for the Müller-Rochow process, which limits the range ofsubstances that can be used, since most substances decompose at suchtempartures.

Some methods for preparing organosilanes are known from the literature.For example, US2002/0082438 A1 describes the synthesis oforganochlorosilanes starting from trichlorosilane, dichlorosilane ordichloromethylsilane. A further starting material used is a compound ofthe formula R²R³CHX, where X═Cl or Br and R² is selected from C₁₋₁₇alkyl, C₁₋₁₀ fluorinated alkyl with partial or complete fluorination,C₁₋₅ alkenyl, (CH₂)_(n)SiMe_(3-m)Cl_(m) (where n=0-2 and m=0-3),(CH₂)_(p)X (where p=1-9 and X═Cl or Br), or ArCH₂X (where Ar=aromaticC₆₋₁₄ hydrocarbon and X═Cl or Br), and R³ is selected from H, C₁₋₆alkyl, Ar(R′)_(q)(where Ar=aromatic C₆₋₁₄ hydrocarbon, R═C₁₋₄ alkyl,halogen, alkoxy or vinyl, q=0-5). Various quaternary phosphonium halidesare used as catalysts. The reaction mechanism is assumed to be adehydrochlorination, with elimination of hydrogen chloride in allreactions.

DE10018101 A1 discloses a method for preparing organochlorosilanesstarting from trichlorosilane, dichlorosilane or dichloromethylsilane. Afurther starting material used is a compound of the formula R²CH₂X,where X═Cl or Br and R² is selected from C₁₋₁₇ alkyl, C₁₋₁₀ fluorinatedalkyl with partial or complete fluorination, C₁₋₅ alkenyl,(CH₂)_(n)SiMe_(3-m)Cl_(m) (where n=0-2 and m=0-3), Ar(R′)_(q) (whereAr=aromatic C₆₋₁₄ hydrocarbon, R═Cl₁₋₄ alkyl, halogen, alkoxy or vinyl,q=0-5), (CH₂)_(p)X (where p=1-9 and X═C or Br), or ArCH₂X (whereAr=aromatic C₆₋₁₄ hydrocarbon and X═Cl or Br). Tertiary amines orphosphines are used as catalysts. The reaction mechanism is assumed tobe a dehydrochlorination, with elimination of hydrogen chloride in allreactions.

US2012/0114544 A1 discloses a method for preparing organochlorosilanesstarting from a silane of the formula HCl₂Si—R¹ (where R¹═Cl, methyl,trichlorosilylmethyl, dichlorosilylmethyl or methyldichlorosilylmethyl).A further starting material used is a compound of the formula R²—SiCl₃(where R²═Cl, linear C₂₋₁₈ alkyl group, isopropyl, isobutyl, tert-butyl,neopentyl, isooctyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl,cyclohexenylmethyl, 2-(2-pyridyl)ethyl, 2-(4-pyridyl)ethyl,bicyclohept-2-yl, bicyclohepten-5-ylethyl, 11-acetoxyundecyl,11-chloroundecyl, phenyl, benzyl, 2-phenylethyl, 1-naphthyl,diphenylmethyl, CH₃(C═O)O(CH₂)_(k) (where k=2, 3, 10),CF₃(CF₂)_(l)CH₂CH₂ (where l=0-12), R⁴-Ph-(CH₂)_(m) (where m=0, 1, 2, 3and R⁴═Cl₄ alkyl group or halogen), Cl—(CH₂)_(n)— (where n=1-12),NC—(CH₂)_(o)— (where o=2-11), CH₂═CH—(CH₂)_(p)— (where p=0-20),Ar¹—CH(Me)—CH₂— (where Ar¹═C₁₋₄ alkyl group, phenyl substituted with ahalogen atom, biphenyl, biphenyl ether, or naphthyl), Ar²—(CH₂)_(q)—(where q=3-18 and Ar²=phenyl, biphenyl, biphenyl ether, naphthyl, orphenanthryl), Cl₃Si—(CH₂)_(r) (where r=0-12),Cl₃Si—(CH₂)_(s)—Ar³—(CH₂)_(s) (where s=0 or 1 and Ar³=phenyl, biphenyl,naphthyl, anthracenyl or2,2,5,5-tetrachloro-4-trichlorosilyl-2,5-disilylcyclohexyl), orAr⁴—(CH₂)_(t)— (where t=0 or 1 and Ar⁴=phenyl, biphenyl, naphthyl, oranthracenyl), trichlorosilyl (Cl₃Si—) or trichlorosilyloxy (Cl₃SiO).Quaternary phosphonium halides are used as the catalyst.

Jung et al. (J. Org. Chem. 692 (2007) 3901-3906) discloses the reactionof trichlorosilane with polychloromethanes such as chloroform and carbontetrachloride. The quaternary phosphonium halide Bu₄PCl is used as thecatalyst. The reaction mechanism is assumed to be a dehydrohalogenation,with elimination of hydrogen chloride in all reactions.

EP 1705180 A1 discloses a method for synthesizingorganothiomethylsilanes starting from a silane of the formula HCl₂Si—R¹(where R¹═H, halogen or C₁₋₆ alkyl). A further starting material used isa compound of the formula R²—S—CH₂—X (where X=halogen and R²═C₁₋₆ alkylor aryl). Quaternary ammonium or phosphonium halides are used as thecatalyst. The reaction mechanism is assumed to be a dehydrohalogenation,with elimination of hydrogen chloride in all reactions.

DE102014118658 A1 describes a method for preparing perhalogenatedcyclohexasilane anion starting from trichlorosilane and dichlorosilane.Quaternary ammonium or phosphonium halides are used as the catalyst. Theformation of hydrogen as a by-product of the synthesis is described.

DE102015105501 A1 describes the synthesis of the followingperchlorinated, anionic, silylated carbon compounds [C(SiCl₃)₃]⁻,[(Cl₃Si)₂C—C(SiCl₃)₂]⁻, [(Cl₃C)₂SiCl₃]⁻, and [Cl₄CSiCl₃]⁻. Achlorocarbon compound of the formula C_(m)H_(4-n)Cl_(n) (where m=1 or 2and n=2-4) is used. The other starting compound, the silane, is limitedto trichlorosilane, hexachlorodisilane and perchlorinatedcyclohexasilane anions. Quaternary ammonium or phosphonium halides instoichiometric amounts are used as catalysts.

It is accordingly the object of the present invention to provide amethod with which (organo)trihalosilanes or trichlorosilane can beproduced economically. In addition, the method should also allow accessto substances that cannot be prepared by the two existing methods.

SUMMARY OF THE INVENTION

These and other objects are achieved by a method for the dehydrogenationof dichlorosilane, wherein dichlorosilane is reacted in the presence ofan ammonium and/or phosphonium salt at a temperature within a range of70-300° C. either with

(A) at least one halogenated hydrocarbon of the formula (I)

R¹—X  (I),

where

X═F, Cl, Br or I; and

R¹=branched or unbranched C₂-C₂₀ alkyl radical,

-   -   branched or unbranched C₂-C₁₃ heteroalkyl radical, the carbon        skeleton containing one or more heteroatoms independently        selected from N, P, S or O,    -   branched or unbranched C₁-C₁₀ fluoroalkyl radical with partial        or complete fluorination,    -   branched or unbranched C₂-C₂₀ alkenyl radical, excluding        C₂H_(4-n)Cl_(n) when n=2-4, branched or unbranched C₂-C₂₀        alkynyl radical,    -   C₃-C₁₄ cycloalkyl radical,    -   C₂-C₁₃ heterocycloalkyl radical, the ring skeleton containing        one or more heteroatoms independently selected from N, P, S or        O,    -   C₆-C₁₄ aryl radical,    -   C₅-C₁₃ heteroaryl radical, the ring skeleton containing one or        more heteroatoms independently selected from N, P, S or O,    -   (CH₂)_(n)—Ar, where Ar═C₆-C₁₄ aryl radical and n=1-5,    -   where all of the above-mentioned radicals may be unsubstituted        or else singly or multiply substituted by halogen, C₁-C₄ alkoxy,        vinyl, phenyl or C₁-C₄ alkyl, methyl radical,    -   (CH₂)_(n)X, where n=1-10 and X═F, Cl, Br or I,    -   R²—S—CH₂ radical, where R²═C₁-C₆ alkyl or C₆-C₁₄ aryl,    -   (CH₂)_(n)SiMe_(3-m)—Cl_(m), where n=0-5 and m=0, 1, 2, 3,    -   (CH₂)_(n)NH(C═O)OCH₃, where n=1-5,    -   (CH₂)_(n)OCH₂ (oxirane), where n=1-5,    -   (CH₂)_(n)O(C═O)(C(CH₃)═CH₂), where n=1-5,    -   (CH₂)_(n)NH₂, where n=1-5,    -   (CH₂)_(n)NH(C═O)NH₂, where n=1-5,    -   (CH₂)_(n)NHR, where n=1-5, and R=cyclohexyl or C₂H₄NH₂;

or

(B) a hydrogen halide.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the method according to the invention, dichlorosilane is reacted witha halogenated hydrocarbon of the formula (I) or with a hydrogen halidein the presence of an ammonium and/or phosphonium salt as catalyst. Bothdichlorosilane and trichlorosilane may be used as reactants in themethod according to the invention. Dichlorosilane is dehydrogenateddirectly by this method. Trichlorosilane, on the other hand, initiallydisproportionates to tetrachlorosilane and dichlorosilane (reactionscheme 1), which then undergoes dehydrogenation.

The dehydrogenation of dichlorosilane proceeds according to reactionscheme 2 below:

In a first reaction step, the non-isolable intermediate [SiCl₃] isformed from dichlorosilane with elimination of hydrogen (reaction scheme2). This anion can either react further through formal nucleophilicsubstitution or it can insert as dichlorosilylene. In the case ofreaction with an R-Cl bond, the product is in both cases a compoundR-SiCl₃ and in both cases a chloride ion is liberated again, which isthen in turn available as a catalyst (reaction scheme 3):

The reaction of the intermediate with a compound R—X (X═F, Br or 1)results in the formation, in addition to a chloride ion, of a compoundR—SiCl_(3-n)X_(n) (n=0, 1, 2 or 3) as a result of halogen exchange atsilicon, which means that a total of 4 products are obtained (reactionscheme 4):

If the intermediate reacts for example with HCl, trichlorosilane isformed and a chloride ion is liberated (reaction scheme 5):

In the method according to the invention, an ammonium and/or phosphoniumsalt is used as catalyst. The ammonium and/or phosphonium salt may alsobe used in immobilized form, for example on a silicone resin, on silica,on an inorganic support or on an organic polymer. The ammonium and/orphosphonium salt may also be formed in situ from an amine or phosphineand HCl.

Quaternary ammonium halides [R₄N]X and phosphonium halides [R₄P]X ortertiary ammonium halides [R₃NH]X are particularly suitable, where thefollowing applies in each case:

X═Cl, Br or I, with preference given to Cl or Br, and

R=independently selected from the group consisting of C₁-C₁₂ alkylgroup, C₁-C₆ alkyl-substituted C₆-C₁₄ aryl group, and phenyl group, withpreference given to ethyl, n-butyl, and phenyl.

Particularly preferred examples of such compounds are [n-Bu₄N]Cl,[Et₄N]Cl, [Ph₄P]Cl, and [n-Bu₄P]Cl.

The reactant used is either a hydrogen halide or a halogenatedhydrocarbon of the formula (I).

Hydrogen halide is understood as meaning hydrogen fluoride, hydrogenchloride, hydrogen bromide or hydrogen iodide, with preference given tohydrogen chloride.

R¹—X  (1)

where

X═F, Cl, Br or I, and

R¹=branched or unbranched C₂-C₂₀ alkyl radical,

-   -   branched or unbranched C₂-C₁₃ heteroalkyl radical, the carbon        skeleton containing one or more heteroatoms independently        selected from N, P, S or O,    -   branched or unbranched C₁-C₁₀ fluoroalkyl radical with partial        or complete fluorination,    -   branched or unbranched C₂-C₂₀ alkenyl radical, excluding        C₂H_(4-n)Cl_(n) when n=2-4, branched or unbranched C₂-C₂₀        alkynyl radical,    -   C₃-C₁₄ cycloalkyl radical,    -   C₂-C₁₃ heterocycloalkyl radical, the ring skeleton containing        one or more heteroatoms independently selected from N, P, S or        O,    -   C₆-C₁₄ aryl radical,    -   C₅-C₁₃ heteroaryl radical, the ring skeleton containing one or        more heteroatoms independently selected from N, P, S or O,    -   (CH₂)_(n)—Ar, where Ar═C₆-C₁₄ aryl radical and n=1-5,    -   where all of the above-mentioned radicals may be unsubstituted        or else singly or multiply substituted by halogen, C₁-C₄ alkoxy,        vinyl, phenyl or C₁-C₄ alkyl, methyl radical,    -   (CH₂)_(n)X, where n=1-10 and X═F, Cl, Br or I,    -   R²—S—CH₂ radical, where R²═C₁-C₆ alkyl or C₆-C₁₄ aryl,    -   (CH₂)_(n)SiMe_(3-m)—Cl_(m), where n=0-5 and m=0, 1, 2, 3,    -   (CH₂)_(n)NH(C═O)OCH₃, where n=1-5,    -   (CH₂)_(n)OCH₂ (oxirane), where n=1-5,    -   (CH₂)_(n)O(C═O)(C(CH₃)═CH₂), where n=1-5,    -   (CH₂)_(n)NH₂, where n=1-5,    -   (CH₂)_(n)NH(C═O)NH₂, where n=1-5,    -   (CH₂)_(n)NHR, where n=1-5, and R=cyclohexyl or C₂H₄NH₂.

R¹ in formula (I) is preferably selected from the group consisting of

branched or unbranched C₂-C₂₀ alkyl radical,

branched or unbranched C₂-C₁₃ heteroalkyl radical, the carbon skeletoncontaining one or more heteroatoms independently selected from N, P, Sor O;

branched or unbranched C₂-C₂₀ alkenyl radical, excluding C₂H_(4-n)Cl_(n)when n=2-4, C₃-C₁₄ cycloalkyl radical,

C₂-C₁₃ heterocycloalkyl radical, the ring skeleton containing one ormore heteroatoms independently selected from N, P, S or O,

(CH₂)_(n)—Ar, where Ar═C₆-C₁₄ aryl radical and n=1-3,

where all of the above-mentioned radicals may be unsubstituted or elsesingly or multiply substituted by halogen, C₁-C₄ alkoxy, vinyl, phenylor C₁-C₄ alkyl,

methyl radical,

(CH₂)_(n)X, where n=1-10 and X═F, Cl, Br or I,

(CH₂)_(n)SiMe_(3-m)—Cl_(m), where n=0-5 and m=0, 1, 2, 3.

Examples of such compounds are:

methyl chloride, ethyl chloride, n-propyl chloride, isopropyl chloride,n-butyl chloride, tert-butyl chloride, isobutyl chloride, sec-butylchloride, n-pentyl chloride, n-pentyl iodide, n-pentyl bromide, n-pentylfluoride, n-octyl chloride, 1-chlorohexadecane, 1,2-dichloroethane,1,1-dichloropropane, 1,2-dichloropropane, 1,3-dichloropropane,monochlorobenzene, benzyl chloride, vinyl chloride, allyl chloride,allyl bromide, 1-chloro-2,4,4-trimethylpentane, hexadecyl chloride,1-chloro-3,3,3-trifluoropropane, trichloro(chloromethyl)silane,dichloro(chloromethyl)silane, trimethyl(chloromethyl)silane,trimethyl(3-chloropropyl)silane, crotyl chloride, 4-fluorobenzylchloride, 4-chlorobenzyl chloride, 4-methoxybenzyl chloride,4-phenylbenzyl chloride, diphenyl-1-dichloromethane,(1-chloroethyl)benzene, cyclopentyl chloride, 1-bromo-3-chloropropane,1,4-dichlorobutane, 1,4-bis(chloromethyl)benzene.

The method according to the invention is carried out at a temperaturewithin a range of 70-300° C. The temperature is preferably within arange of 100-300° C., more preferably within a range of 100-180° C., andyet more preferably within a range of 150-180° C. Most preferably. thetemperature is within a range of 170-180° C.

The molar ratio of hydrogen halide or halogenated hydrocarbon todichlorosilane may be freely chosen by those skilled in the art.

In the case of hydrogen halide as the reactant, the amount of hydrogenhalide added preferably corresponds to the stoichiometric amount ofdichlorosilane to be converted. In the case of all other reactants, thestoichiometric amount of dichlorosilane formally used preferablycorresponds to at least the amount of R¹—X bonds to be silylated. If notall the R¹—X bonds are to be silylated, the compound R¹—X is preferablyused in a suprastoichiometric amount. The molar ratio of dichlorosilaneto hydrogen halide or halogenated hydrocarbon is particularly preferablywithin a range from 1:1 to 1:10 based on the amount of R¹—X bonds.

The molar ratio of catalyst to dichlorosilane may be freely chosen bythose skilled in the art.

The molar ratio is preferably within a range from 0.01:1 to 0.2:1.

The method according to the invention for the dehydrogenation ofdichlorosilane allows organosilanes to be prepared in an economicalmanner. The method also enables dichlorosilane to be converted intotrichlorosilane. On the one hand, the dichlorosilane formed as aby-product in the chlorosilane process can in principle be convertedinto the main product trichlorosilane in this way. Alternatively,mixtures of the two substances may be worked up such that the proportionof dichlorosilane in the mixture is lowered or the mixture is completelyconverted into trichlorosilane.

EXAMPLES

GC measurements were performed using an Agilent 6890N (WLD detector;columns: HP5 from Agilent: length: 30 m/diameter: 0.32 mm/filmthickness: 0.25 μm; RTX-200 from Restek: length: 60 m/diameter: 0.32mm/film thickness: 1 μm). Retention times were compared with thecommercially available substances, all chemicals were used as purchased.MS measurements were carried out using a ThermoStar™ GSD 320 T2 with aniridium cathode.

Reactions Starting from Trichlorosilane

Example 1: Synthesis of trichloromethylsilane

An autoclave was filled with HSiCl₃ (50 g; 0.37 mol), [n-Bu₄N]Cl (0.2 g;0.7 mmol), and MeCl (9.4 g; 0.19 mol). The autoclave was heated to 140°C. for 13 h. After cooling, approx. 10 bar pressure remained in theautoclave. The product mixture consisted of 30% by weight of Cl₃SiMe,50% by weight of SiCl₄, and 20% by weight of HSiCl₃, in addition towhich traces of MeCl and H₂SiCl₂ were detectable. The gas evolved in thereaction was unambiguously identified as hydrogen by mass spectrometry.

Example 2: Synthesis of n-propyltrichlorosilane

An autoclave was filled with HSiCl₃ (40 g; 0.30 mol), [n-Bu₄P]Cl (2 g;6.8 mmol), and MeCH₂CH₂Cl (10 g; 0.13 mol). The autoclave was heated to175° C. for 13 h. After cooling, approx. 20 bar pressure remained in theautoclave. The product mixture consisted of 48% by weight ofCl₃SiCH₂CH₂Me, 42% by weight of SiCl₄, 8% by weight of HSiCl₃, and 2% byweight of MeCH₂CH₂Cl, in addition to which traces of H₂SiCl₂ weredetectable. The gas evolved in the reaction was unambiguously identifiedas hydrogen by mass spectrometry.

Example 3: Synthesis of 1-chloro-3-trichlorosilylpropane and 1,3-bis(trichlorosilyl)propane

An autoclave was filled with HSiCl₃ (36.6 g; 0.27 mol), [n-Bu₄P]Cl (2 g;6.8 mmol), and Cl—CH₂CH₂CH₂—Cl (15.4 g; 0.13 mol). The autoclave washeated to 170° C. for 13 h. After cooling, approx. 10 bar pressureremained in the autoclave. The product mixture consisted of 25% byweight of ClSiCH₂CH₂CH₂Cl, 14% by weight of ClSiCH₂CH₂CH₂SiCl, 14% byweight of ClCH₂CH₂CH₂Cl, 45% by weight of SiCl₄, 2% by weight of HSiCl₃,and traces of H₂SiCl₂. The gas evolved in the reaction was unambiguouslyidentified as hydrogen by mass spectrometry.

Example 4: Synthesis of 1-chloro-3-trichlorosilylpropane

An autoclave was filled with HSiCl₃ (18 g; 0.13 mol), [n-Bu₄P]Cl (2 g;6.8 mmol), and Cl—CH₂CH₂CH₂—Cl (30.2 g; 0.27 mol). The autoclave washeated to 170° C. for 13 h. After cooling, approx. 5 bar pressureremained in the autoclave. The product mixture consisted of 21% byweight of ClSiCH₂CH₂CH₂Cl, 1% by weight of ClSiCH₂CH₂CH₂SiCl, 59% byweight of ClCH₂CH₂CH₂Cl, 19% by weight of SiCl₄, and traces of H₂SiCl₂.The gas evolved in the reaction was unambiguously identified as hydrogenby mass spectrometry.

Example 5: Synthesis of allyltrichlorosilane

An autoclave was filled with HSiCl₃ (20 g; 0.15 mol), [n-Bu₄P]Cl (2 g;6.8 mmol), and allyl chloride (11.2 g; 0.15 mol). The autoclave washeated to 150° C. for 13 h. After cooling, approx. 15 bar pressureremained in the autoclave. The product mixture consisted of 42% byweight of Cl₃SiCH₂CHCH₂, 40% by weight of SiCl₄, 18% by weight ofClCH₂CHCH₂, and traces of H₂SiCl₂. The gas evolved in the reaction wasunambiguously identified as hydrogen by mass spectrometry.

Reactions Starting from Dichlorosilane

Example 6a) Synthesis of n-propyltrichlorosilane

An autoclave was filled with H₂SiCl₂ (27 g; 0.27 mol), [n-Bu₄P]Cl (2.5g; 8 mmol), and MeCH₂CH₂Cl (49.5 g; 0.63 mol). The autoclave was heatedto 175° C. for 13 h. After cooling, approx. 45 bar pressure remained inthe autoclave. The product mixture consisted of 50% by weight ofCl₃SiCH₂CH₂Me, 2% by weight of SiCl₄, 2% by weight of HSiCl₃, and 46% byweight of MeCH₂CH₂Cl, in addition to which traces of H₂SiCl₂ weredetectable. The gas evolved in the reaction was unambiguously identifiedas hydrogen by mass spectrometry.

Example 6b) Synthesis of n-pentyltrichlorosilane

An autoclave was filled with H₂SiCl₂ (15 g; 0.15 mol), [n-Bu₄P]Cl (2.5g; 8 mmol), and Me(CH₂)₄Cl (50.5 g; 0.48 mol). The autoclave was heatedto 177° C. for 13 h. After cooling, approx. 13 bar pressure remained inthe autoclave. The product mixture consisted of 45% by weight ofCl₃Si(CH₂)₄Me and 55% by weight of Me(CH₂)₄Cl, in addition to whichtraces of H₂SiCl₂ were detectable. The gas evolved in the reaction wasunambiguously identified as hydrogen by mass spectrometry.

Example 6c) Synthesis of n-pentyltrihalosilane Starting from1-iodopentane

An autoclave was filled with H₂SiCl₂ (11 g; 0.11 mol), [n-Bu₄P]Cl (2.0g; 7 mmol), and Me(CH₂)₄I (27.5 g; 0.14 mol). The autoclave was heatedto 175° C. for 13 h. After cooling, approx. 16 bar pressure remained inthe autoclave. The product mixture consisted of 80% by weight of amixture of Cl_(3-n)I_(n)Si(CH₂)₄Me (n=0-3) and 20% by weight ofMe(CH₂)₄I , in addition to which traces of H₂SiCl₂ were detectable. Thegas evolved in the reaction was unambiguously identified as hydrogen bymass spectrometry.

Example 6d) Synthesis of n-pentyltrihalosilane Starting from1-bromopentane

An autoclave was filled with H₂SiCl₂ (26 g; 0.26 mol), [n-Bu₄P]Cl (2.0g; 7 mmol), and Me(CH₂)₄Br (40.0 g; 0.27 mol). The autoclave was heatedto 170° C. for 13 h. After cooling, approx. 33 bar pressure remained inthe autoclave. The product mixture consisted of 100% by weight of amixture of Cl_(3-n)Br_(n)Si(CH₂)₄Me (n=0-3), in addition to which tracesof H₂SiCl₂ were detectable. The gas evolved in the reaction wasunambiguously identified as hydrogen by mass spectrometry.

Example 6e) Synthesis of n-pentyltrihalosilane Starting from1-fluoropentane

An autoclave was filled with H₂SiCl₂ (26 g; 0.26 mol), [n-Bu₄P]Cl (2.0g; 7 mmol), and Me(CH₂)₄F (23.5 g; 0.26 mol). The autoclave was heatedto 170° C. for 13 h. After cooling, approx. 10 bar pressure remained inthe autoclave. The product mixture consisted of 100% by weight of amixture of Cl_(3-n)F_(n)Si(CH₂)₄Me (n=0-3), in addition to which tracesof H₂SiCl₂ were detectable. The gas evolved in the reaction wasunambiguously identified as hydrogen by mass spectrometry.

Example 7a) Reaction of dichlorosilane with HCl

An autoclave was filled with H₂SiCl₂ (17 g; 0.17 mol), HCl (6.2 g; 0.17mol), [n-Bu₄P]Cl (2.0 g; 7 mmol), and HSiCl₃ (20 g; 0.25 mol). Theautoclave was heated to 180° C. for 13 h. After cooling, approx. 19 barpressure remained in the autoclave. The product consisted of 100% byweight of HSiCl₃, in addition to which traces of H₂SiCl₂ weredetectable. The gas evolved in the reaction was unambiguously identifiedas hydrogen by mass spectrometry, in addition to which traces of HClwere detectable.

Example 7b) Reaction of Dichlorosilane with HCl

An autoclave was filled with H₂SiCl₂ (17 g; 0.17 mol), HCl (6.2 g; 0.17mol), Bu₃N (1.0 g; 5 mmol), and HSiCl₃ (20 g; 0.15 mol). The autoclavewas heated to 180° C. for 13 h. After cooling, approx. 19 bar pressureremained in the autoclave. The product consisted of 100% by weight ofHSiCl₃, in addition to which traces of H₂SiCl₂ were detectable. The gasevolved in the reaction was unambiguously identified as hydrogen by massspectrometry, in addition to which traces of HCl were detectable.

1.-11. (canceled)
 12. A method for the dehydrogenation of dichlorosilanein which hydrogen is formed, comprising: reacting dichlorosilane in thepresence of an ammonium and/or phosphonium salt at a temperature withina range of 70-300° C., either with (A) at least one halogenatedhydrocarbon of the formula (I)R¹—X  (I), where X is F, Cl, Br or I; and R¹ is a branched or unbranchedC₂-C₂₀ alkyl radical, a branched or unbranched C₂-C₁₃ heteroalkylradical, the carbon skeleton of which contains one or more heteroatomsindependently selected from N, P, S or O, a branched or unbranchedC₁-C₁₀ fluoroalkyl radical with partial or complete fluorination, abranched or unbranched C₂-C₂₀ alkenyl radical, excluding C₂H_(4-n)Cl_(n)radicals where n is 2-4, a branched or unbranched C₂-C₂₀ alkynylradical, a C₃-C₁₄ cycloalkyl radical, a C₂-C₁₃ heterocycloalkyl radical,the ring skeleton of which contains one or more heteroatomsindependently selected from N, P, S or O, a C₆-C₁₄ aryl radical, aC₅-C₁₃ heteroaryl radical, the ring skeleton of which contains one ormore heteroatoms independently selected from N, P, S or O, and/or(CH₂)_(n)—Ar, where Ar is a C₆-C₁₄ aryl radical and n is 1-5, where allof the above-mentioned radicals may be unsubstituted or else singly ormultiply substituted by halogen, C₁-C₄ alkoxy, vinyl, phenyl or C₁-C₄alkyl, radicals, (CH₂)_(n)X, where n is 1-10 and X is F, Cl, Br or I,R²—S—CH₂ radicals, where R² is C₁-C₆ alkyl or C₆-C₁₄ aryl,(CH₂)_(n)SiMe_(3-m)—Cl_(m), where n is 0-5 and m is 0, 1, 2, 3,(CH₂)_(n)NH(C═O)OCH₃, where n is 1-5, (CH₂)_(n)OCH₂ (oxirane), where nis 1-5, (CH₂)_(n)O(C═O)(C(CH₃)═CH₂), where n is 1-5, (CH₂)_(n)NH₂, wheren is 1-5, (CH₂)_(n)NH(C═O)NH₂, where n is 1-5, and (CH₂)_(n)NHR, wheren=1-5, and R is cyclohexyl or C₂H₄NH₂; or with (B) a hydrogen halide,wherein the molar ratio of dichlorosilane to hydrogen halide orhalogenated hydrocarbon is within a range from 1:1 to 1:10.
 13. Themethod of claim 12, wherein the temperature is within the range of100-300° C.
 14. The method of claim 12, wherein the molar ratio ofcatalyst to dichlorosilane is within the range from 0.01:1 to 0.2:1. 15.The method of claim 12, wherein a hydrogen halide is present, and thehydrogen halide is hydrogen chloride.
 16. The method of claim 12,wherein the ammonium and/or phosphonium salt is a quaternary ammoniumhalide [R₄N]X, a phosphonium halide [R₄P]X, or a tertiary ammoniumhalide [R₃NH]X, where X is Cl, Br or I.
 17. The method of claim 16,wherein the ammonium and/or phosphonium salt is selected from the groupconsisting of [n-Bu₄N]Cl, [Et₄N]Cl, [Ph₄P]Cl, [n-Bu₄P]Cl, and mixturesthereof.
 18. The method of claim 12, wherein R¹ is selected from thegroup consisting of branched or unbranched C₂-C₂₀ alkyl radicals, abranched or unbranched C₂-C₁₃ heteroalkyl radical, the carbon skeletonof which contains one or more heteroatoms independently selected from N,P, S or O; a branched or unbranched C₂-C₂₀ alkenyl radical, excludingC₂H_(4-n)Cl_(n) when n is 2-4, a C₃-C₁₄ cycloalkyl radical, a C₂-C₁₃heterocycloalkyl radical, the ring skeleton of which contains one ormore heteroatoms independently selected from N, P, S or O, and(CH₂)_(n)—Ar, where Ar is a C₆-C₁₄ aryl radical and n is 1-3, where allof the above-mentioned radicals may be unsubstituted or else singly ormultiply substituted by halogen, C₁-C₄ alkoxy, vinyl, phenyl or C₁-C₄alkyl, (CH₂)_(n)X, where n is 1-10 and X is F, Cl, Br or I,(CH₂)_(n)SiMe_(3-m)—Cl_(m), where n is 0-5 and m is 0, 1, 2,
 3. 19. Themethod of claim 12, wherein the halogenated hydrocarbon is selected fromthe group consisting of methyl chloride, ethyl chloride, n-propylchloride, isopropyl chloride, n-butyl chloride, tert-butyl chloride,isobutyl chloride, sec-butyl chloride, n-pentyl chloride, n-pentyliodide, n-pentyl bromide, n-pentyl fluoride, n-octyl chloride,1-chlorohexadecane, 1,2-dichloroethane, 1,1-dichloropropane,1,2-dichloropropane, 1,3-dichloropropane, monochlorobenzene, benzylchloride, vinyl chloride, allyl chloride, allyl bromide,1-chloro-2,4,4-trimethylpentane, hexadecyl chloride,1-chloro-3,3,3-trifluoropropane, trichloro(chloromethyl)silane,dichloro(chloromethyl)silane, trimethyl(chloromethyl)silane,trimethyl(3-chloropropyl)silane, crotyl chloride, 4-fluorobenzylchloride, 4-chlorobenzyl chloride, 4-methoxybenzyl chloride,4-phenylbenzyl chloride, diphenyl-1-dichloromethane,(1-chloroethyl)benzene, cyclopentyl chloride, 1-bromo-3-chloropropane,1,4-dichlorobutane, 1,4-bis(chloromethyl)benzene, and mixtures thereof.20. The method of claim 12, wherein dichlorosilane is formed in situ bydisproportionation of trichlorosilane.
 21. The method of claim 12,wherein the method is operated continuously or batchwise.